Search results for "liquid"

Nonisothermal elongational behavior of blends with liquid crystalline polymers

1994

Measurements of melt strength and breaking stretching ratio of several blends of thermoplastic polymers with liquid crystalline polymers are presented. The melt strength behavior depends not only on the viscosity of the blends but also on the temperature dependence of the viscosity. In particular, even if the viscosities of the blends are, at the extrusion temperature, lower than that of the thermoplastic matrices, the melt strength can be larger than that of the pure thermoplastics if its viscosity-temperature curve exceeds that of the matrices far from the solidification temperature. This behavior allows one to spin or film blow these blends despite the low viscosity.

Shear flow characterization of blends containing liquid crystal polymers

1992

A simple phenomenological approach is proposed in order to predict the presence of minima in the viscosity-composition curves of blends of thermoplastic with liquid crystal polymer (LCP). When the viscosity of the liquid crystal polymer is larger than that of the thermoplastic matrix, a minimum is observed. A possible explanation of the presence of yield stress in the flow curves of these blends is also given.

Heterogeneous oxidation of pyrimidine and alkyl thioethers in ionic liquids over mesoporous Ti or Ti/Ge catalysts.

2004

Heterogeneous catalytic oxidation of a series of thioethers (2-thiomethylpyrimidine, 2-thiomethyl-4,6-dimethyl-pyrimidine, 2-thiobenzylpyrimidine, 2-thiobenzyl-4,6-dimethylpyrimidine, thioanisole, and n-heptyl methyl sulfide) was performed in ionic liquids by using MCM-41 and UVM-type mesoporous catalysts containing Ti, or Ti and Ge. A range of triflate, tetrafluoroborate, trifluoroacetate, lactate and bis(trifluoromethanesulfonyl)-imide-based ionic liquids were used. The oxidations were carried out by using anhydrous hydrogen peroxide or the urea-hydrogen peroxide adduct and showed that ionic liquids are very effective solvents, achieving greater reactivity and selectivity than reactions p…

A counterion study of a series of [Cu(P^P)(N^N)][A] compounds with bis(phosphane) and 6-methyl and 6,6′-dimethyl-substituted 2,2′-bipyridine ligands …

2021

The syntheses and characterisations of a series of heteroleptic copper(i) compounds [Cu(POP)(Mebpy)][A], [Cu(POP)(Me2bpy)][A], [Cu(xantphos)(Mebpy)][A] and [Cu(xantphos)(Me2bpy)][A] in which [A]− is [BF4]−, [PF6]−, [BPh4]− and [BArF4]− (Mebpy = 6-methyl-2,2′-bipyridine, Me2bpy = 6,6′-dimethyl-2,2′-bipyridine, POP = oxydi(2,1-phenylene)bis(diphenylphosphane), xantphos = (9,9-dimethyl-9H-xanthene-4,5-diyl)bis(diphenylphosphane), [BArF4]− = tetrakis(3,5-bis(trifluoromethyl)phenyl)borate) are reported. Nine of the compounds have been characterised by single crystal X-ray crystallography, and the consequences of the different anions on the packing interactions in the solid state are discussed. T…

1979

Pressure influences on the viscosity of polymer solutions

1982

Of all physico-chemical quantities characterizing the behavior of liquids, the viscosity coefficient η is normally most sensitive to pressure. Early measurements of η(p) date back almost 100 years [1] but they were carried out with very different objectives [2]. Currently, one is particularly interested in polymer solutions, for instance because of the additives to motor oils and of oil recovery. The present paper reports on measurements with polystyrenes of high molecular uniformity in eight different solvents. It confines itself to zero-shear viscosities and discusses the possibilities of discovering the influence of pressure via the molecular structure of the solvent and via its thermody…

1985

Eye Cataract Simulation Using Polymer Dispersed Liquid Crystal Scattering Obstacles

2004

Polymer dispersed liquid crystals with electrically induced variations of light scattering extent similar to that of transparent PLZT ceramics are used for simulation of different development stages of eye cataract. Wavelength dependencies of scattering are determined in the visible spectral range, and human visual response looking through the scattering obstacle to the onset of various spatial frequency stimuli is determined psychophysically and electrophysiologically in order to find correlation between the scattering extent, visual acuity and visual evoked potential VEP chromatic characteristics.

Structures, properties and miscibility behaviour of liquid crystalline polycatenar tetrone derivatives

1995

Abstract The tetrones represent an interesting new mesogenic building block. The results of this study show that they can be incorporated into a variety of mesophases. A smectic phase was observed in the polycatenar compound with four terminal chains as expected. The phase exhibits a tilted structure (Sc phase) to prevent void formation. The compound with six pendant chains forms a columnar phase. In spite of their structural similarity, the tetrones studied tended not to be completely miscible. However, complete miscibility with a semi-discoid phenylhydrazone was observed. When this hydrazone, which forms a columnar ‘Dho phase’, was mixed with tetrone which forms a columnar ‘Dhd phase’ a c…

Factors influencing the transport of tryptophan hydrochloride through supported liquid membranes containing macrocyclic carriers

1997

Commercially available PTFE membranes were used as a support for liquid membranes in amino acid transport. Using tryptophan as a model amino acid, the influence of the type of organic liquid, kind of macrocyclic carrier and counter-ion on transport efficiency was examined. These studies show the strong influence of the kind of the counter-ion co-transported with amino acid cation, and the type of macrocyclic carrier used on the transport efficiency. The transport efficiency depends also on the pH of the source phase and on the nature of the organic liquid used as a membrane solvent. Liquid membranes supported on commercial porous-PTFE-membranes with hydrophobic solvents are stable for more …